C Programming-Lecture Notes-03-Variables.pdf

B.Bhuvaneswaran, AP (SG) / CSE
9791519152
bhuvaneswaran@rajalakshmi.edu.in
Programming Logic
Variables

Variables
Variables Rajalakshmi Engineering College 2
Rajalakshmi Engineering College 2
Variables
 A variable is a data name used for storing a data value. Its value
may be changed during the program execution. It has memory
location and can store a single value at a time.

Variables
Examples
Value 143 A 18.75
Variable Name count letter temperature
Type
Integer
(int)
Character
(char)
Floating Point
(float)

Variables
Rules for Naming Variables
 A variable name is any combination of alphabets, digits or underscores.
 A variable must begin with a character without spaces but an
underscore is permitted.
 Maximum characters recognized is 31 (compiler dependent). The length
of the variable varies from compiler to compiler.
 Keywords cannot be used as variable names.
 Variable names are case sensitive.
 The variable names may be a combination of uppercase and lowercase
characters. For example, suM and sum are not the same.
 Blanks and commas are not permitted within a variable name.
 No special characters (other than an underscore) are used in a variable
name.

Variables
Examples
 Valid Examples:
AVERAGE height subject1 n1
City male_sum fact n
 Invalid Examples:
char price$ group one 786

Variables
Declaration of variables
 The declaration of variables must be done before they are used in
the program.
 It tells the compiler what the variable name is and it specifies
what type of data the variable will hold.
 A variable declaration consists of a data type name followed by a
list of one or more variables of that type separated by commas.
 Syntax:
datatype var1, var2, . . . varN;
 where var1, var2, . . .varN are the names of the variables.

Variables
Examples
 Valid Examples:
int sum;
int mark1, mark2, mark3;
float basicpay, netpay;
char gender;
 Where int, float and char are the keywords to represent integer,
real and character data values respectively.

Variables
Points to Remember
 The variables will contain some garbage value when they are
declared.
Value -123 -75 14246 258 -31.26 28.11 X
Name sum mark1 mark2 mark3 basicpay netpay gender

Variables
Assigning Values to Variables
 Values can be assigned to variables using the assignment operator
=.
 Syntax:
variable_name = value;
 An assignment statement implies that the value of the variable on
the left of the ‘equal sign’ is set equal to the value of the quantity
(or expression) on the right.

Variables
Assigning the Values
 sum = 100;
 mark1 = 75;
 mark2 = 80;
 mark3 = 85;
 basicpay = 30000.00;
 netpay = basicpay – 5000.00;
 gender = 'M';
Value 100 75 80 85 30000.000000 25000.000000 M
Name sum mark1 mark2 mark3 basicpay netpay Gender

Variables
Assigning the Values
 It is also possible to assign a value to a variable at the time the
variable is declared. This takes the following form:
datatype variable_name = value (or) variable (or) expression;

Variables
Examples
 int sum = 100;
 int mark1 = 75;
 int mark2 = 80;
 int mark3 = 85;
 float basicpay = 30000.00;
 float netpay = basicpay – 5000.00;
 char gender = 'M';
Value 100 75 80 85 30000.000000 25000.000000 M
Name sum mark1 mark2 mark3 basicpay netpay Gender

Variables
Initialization of Variables
 The process of giving an initial value to variables is called
initialization.
 C permits the initialization of more than one variable in one
statement using multiple assignment operators.

Variables
Initialization of Variables
 Example:
a = b = c = 0;
x = y = z = 1;
 Assigning the values:
Value 0 0 0 1 1 1
Name a b c x y z

Variables
Data Types and Keywords
Data type Keyword
Character char
Unsigned character unsigned char
Signed character signed char
Signed integer signed int (or) int
Signed short integer signed short int (or) short int (or) short
Signed long integer signed long int (or) long int (or) long
Unsigned integer unsigned int (or) unsigned
Unsigned short integer unsigned short int (or) unsigned short
Unsigned long integer unsigned long int (or) unsigned long
Floating point float
Double-precision floating point double
Extended double-precision floating point long double

Variables
Points to Remember
 When an adjective (qualifier) short, long or unsigned is used with
a basic data type specifier, C compilers treat the data type as int.
 If we want to declare a character variable as unsigned, then we
must do so using both the terms unsigned char.

C Programming-Lecture Notes-03-Variables.pdf

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